Effect of thermal load on the behavior of an adjacent precast, prestressed concrete box-beam bridge that contains ultra-high-performance concrete shear keys with transverse dowels

摘要

Adjacent precast, prestressed concrete box-beam bridges have been in service for many years and have historically performed well. There are many advantages to this type of bridge, including a relatively simple design, ease and speed of construction, and high torsional rigidity. The adjacent box-beam bridge consists of box beams placed side by side and connected with partial- or full-depth shear keys, which are normally grouted using nonshrink grout. Typically, tie rods or transverse post-tensioning, with or without a reinforced concrete deck, are used to enhance the continuity of the bridge in the transverse direction. However, reflective cracks in the overlays or in the composite deck due to the longitudinal cracks in the shear keys have become a critical issue. The main functions of shear keys are to transfer the load and prevent the penetration of water between adjacent beams, which can cause degradation of the shear keys and lead to structural and durability issues. The structural issue is the potential reduction in or loss of load transfer, while durability issues could result from salt water penetrating the longitudinal connections, causing corrosion of the beams' reinforcement. Stresses from temperature have been found to be the main cause of longitudinal cracks in shear keys.